Angiogenesis is Differentially Modulated by Anthocyanin and Phenolic Acid Extracts from Wild Blueberry (V. angustifolium) Through PI3K Pathway

Wild blueberries rank very high in anthocyanins (ACNs) and phenolic acids (PA) among other berries. Previous work from our group has documented their beneficial effects. In this study, human umbilical vein endothelial cells were used, and ACNs, PAs, and their combination (ACNs:PAs) at concentrations of 0.002, 8, 15, 60, and 120 μg/mL were tested for endothelial tube formation. Treatment with ACNs decreased, while treatment with PAs and ACNs:PAs increased overall endothelial cell tube formation compared to control. Endothelial cells exposed to ACNs downregulated gene expression of AKT1 and endothelial nitric oxide synthase (eNOS), while PAs upregulated AKT1 and vascular endothelial growth factor (VEGF) gene expression. Combination of ACNs:PAs decreased gene expression of AKT1 and eNOS, while protein levels of AKT1 increased. In summary, based on the type of wild blueberry extract, angiogenesis is differentially modulated and is concentration dependent. Further experiments will delineate the mechanism(s) of the differential action of the aforementioned extracts on angiogenesis.

18F-Trifluoromethanesulfinate Enables Direct C-H 18F-Trifluoromethylation of Native Aromatic Residues in Peptides

18F labeling strategies for unmodified peptides with [18F]fluoride require 18F-labeled prosthetics for bioconjugation more often with cysteine thiols or lysine amines. Here we explore selective radical chemistry to target aromatic residues applying C-H 18F-trifluoromethylation. We report a one-step route to [18F]CF3SO2NH4 from [18F]fluoride and its application to direct [18F]CF3 incorporation at tryptophan or tyrosine residues using unmodified peptides as complex as recombinant human insulin. The fully automated radiosynthesis of octreotide[Trp(2-CF218F)] enables in vivo positron emission tomography imaging.

Preclinical evaluation of [18F]FB-A20FMDV2 as a selective marker for measuring αVβ6 integrin occupancy using positron emission tomography in rodent lung

Purpose

Integrin α_vβ₆ belongs to the RGD subset of the integrin family, and its expression levels are a prognostic and theranostic factor in some types of cancer and pulmonary fibrosis. This paper describes the GMP radiolabelling of the synthetic 20 amino acid peptide A20FMDV2 (NAVPNLRGDLQVLAQKVART), derived from the foot-and-mouth disease virus, and characterises the use of [¹⁸F]FB-A20FMDV2 as a high affinity, specific and selective PET radioligand for the quantitation and visualisation of α_vβ₆ in rodent lung to support human translational studies.

Methods

The synthesis of [¹⁸F]FB-A20FMDV2 was performed using a fully automated and GMP-compliant process. Sprague-Dawley rats were used to perform homologous (unlabelled FB-A20FMDV2) and heterologous (anti-α_vβ₆ antibody 8G6) blocking studies. In order to generate a dosimetry estimate, tissue residence times were generated, and associated tissue exposure and effective dose were calculated using the Organ Level Internal Dose Assessment/Exponential Modelling (OLINDA/EXM) software.

Results

[¹⁸F]FB-A20FMDV2 synthesis was accomplished in 180 min providing ~800 MBq of [¹⁸F]FB-A20FMDV2 with a molar activity of up to 150 GBq/μmol and high radiochemical purity (> 97%). Following i.v. administration to rats, [¹⁸F]FB-A20FMDV2 was rapidly metabolised with intact radiotracer representing 5% of the total radioactivity present in rat plasma at 30 min. For the homologous and heterologous block in rats, lung-to-heart SUV ratios at 30–60 min post-administration of [¹⁸F]FB-A20FMDV2 were reduced by 38.9 ± 6.9% and 56 ± 19.2% for homologous and heterologous block, respectively. Rodent biodistribution and dosimetry calculations using OLINDA/EXM provided a whole body effective dose in humans 33.5 μSv/MBq.

Conclusion

[¹⁸F]FB-A20FMDV2 represents a specific and selective PET ligand to measure drug-associated αvβ6 integrin occupancy in lung. The effective dose, extrapolated from rodent data, is in line with typical values for compounds labelled with fluorine-18 and combined with the novel fully automated and GMP-compliant synthesis and allows for clinical use in translational studies.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04653-5) contains supplementary material, which is available to authorized users.

Phenolic and anthocyanin fractions from wild blueberries (V. angustifolium) differentially modulate endothelial cell migration partially through RHOA and RAC1

The present study investigates the effect of anthocyanin (ACN), phenolic acid (PA) fractions, and their combination (ACNs:PAs) from wild blueberry powder (Vaccinum angustifolium) on the speed of endothelial cell migration, gene expression, and protein levels of RAC1 and RHOA associated with acute exposure to different concentrations of ACNs and PAs. Time-lapse videos were analyzed and endothelial cell speed was calculated. Treatment with ACNs at 60 μg/mL inhibited endothelial cell migration rate ( P ≤ 0.05) while treatment with PAs at 0.002 μg/mL ( P ≤ 0.0001), 60 μg/mL ( P ≤ 0.0001), and 120 μg/mL ( P ≤ 0.01) significantly increased endothelial cell migration rate compared with control. Moreover, exposure of HUVECs to ACNs:PAs at 8:8 μg/mL ( P ≤ 0.05) and 60:60 μg/mL increased ( P ≤ 0.001) endothelial cell migration. Gene expression of RAC1 and RHOA significantly increased 2 hours after exposure with all treatments. No effect of the above fractions was observed on the protein levels of RAC1 and RHOA. Findings suggest that endothelial cell migration is differentially modulated based on the type of blueberry extract (ACN or PA fraction) and is concentration-dependent. Future studies should determine the mechanism of the differential action of the above fractions on endothelial cell migration.

In vivo imaging of microglial activation by positron emission tomography with [(11)C]PBR28 in the 5XFAD model of Alzheimer's disease

Microglial activation has been linked with deficits in neuronal function and synaptic plasticity in Alzheimer's disease (AD). The mitochondrial translocator protein (TSPO) is known to be upregulated in reactive microglia. Accurate visualization and quantification of microglial density by PET imaging using the TSPO tracer [(11)C]-R-PK11195 has been challenging due to the limitations of the ligand. In this study, it was aimed to evaluate the new TSPO tracer [(11)C]PBR28 as a marker for microglial activation in the 5XFAD transgenic mouse model of AD. Dynamic PET scans were acquired following intravenous administration of [(11)C]PBR28 in 6-month-old 5XFAD mice and in wild-type controls. Autoradiography with [(3)H]PBR28 was carried out in the same brains to further confirm the distribution of the radioligand. In addition, immunohistochemistry was performed on adjacent brain sections of the same mice to evaluate the co-localization of TSPO with microglia. PET imaging revealed that brain uptake of [(11)C]PBR28 in 5XFAD mice was increased compared with control mice. Moreover, binding of [(3)H]PBR28, measured by autoradiography, was enriched in cortical and hippocampal brain regions, coinciding with the positive staining of the microglial marker Iba-1 and amyloid deposits in the same areas. Furthermore, double-staining using antibodies against TSPO demonstrated co-localization of TSPO with microglia and not with astrocytes in 5XFAD mice and human post-mortem AD brains. The data provided support of the suitability of [(11)C]PBR28 as a tool for in vivo monitoring of microglial activation and assessment of treatment response in future studies using animal models of AD.

A two-step fluorinase enzyme mediated 18F labelling of an RGD peptide for positron emission tomography

Fluorine-18 radiolabelling of a peptide is conducted in water (pH 7.8 and 37 °C) using the fluorinase enzyme and a ‘click’ reaction.

A localized tolerance in the substrate specificity of the fluorinase enzyme enables "last-step" 18F fluorination of a RGD peptide under ambient aqueous conditions

A strategy for last-step (18)F fluorination of bioconjugated peptides is reported that exploits an "Achilles heel" in the substrate specificity of the fluorinase enzyme. An acetylene functionality at the C-2 position of the adenosine substrate projects from the active site into the solvent. The fluorinase catalyzes a transhalogenation of 5'-chlorodeoxy-2-ethynyladenosine (ClDEA) to 5'-fluorodeoxy-2-ethynyladenosine (FDEA). Extending a polyethylene glycol linker from the terminus of the acetylene allows the presentation of bioconjugation cargo to the enzyme for (18)F labelling. The method uses an aqueous solution (H2(18)O) of [(18)F]fluoride generated by the cyclotron and has the capacity to isotopically label peptides of choice for positron emission tomography (PET).

Effect of chronic antipsychotic treatment on striatal phosphodiesterase 10A levels: a [¹¹C]MP-10 PET rodent imaging study with ex vivo confirmation

A number of phosphodiesterase 10A (PDE10) inhibitors are about to undergo clinical evaluation for their efficacy in treating schizophrenia. As phosphodiesterases are in the same signalling pathway as dopamine D2 receptors, it is possible that prior antipsychotic treatment could influence these enzyme systems in patients. Chronic, in contrast to acute, antipsychotic treatment has been reported to increase brain PDE10A levels in rodents. The aim of this study was to confirm these findings in a manner that can be translated to human imaging studies to understand its consequences. Positron emission tomography (PET) scanning was used to evaluate PDE10A enzyme availability, after chronic haloperidol administration, using a specific PDE10A ligand ([(11)C]MP-10). The binding of [(11)C]MP-10 in the striatum and the cerebellum was measured in rodents and a simplified reference tissue model (SRTM) with cerebellum as the reference region was used to determine the binding potential (BPND). In rats treated chronically with haloperidol (2 mg kg(-1) per day), there was no significant difference in PDE10A levels compared with the vehicle-treated group (BPND±s.d.: 3.57 ± 0.64 versus 2.86 ± 0.71). Following PET scans, ex vivo analysis of striatal brain tissue for PDE10A mRNA (Pde10a) and PDE10A enzyme activity showed no significant difference. Similarly, the PDE10A protein content determined by western blot analysis was similar between the two groups, contrary to an earlier finding. The results of the study indicate that prior exposure to antipsychotic medication in rodents does not alter PDE10A levels.

Characterising the plasma-target occupancy relationship of the neurokinin antagonist GSK1144814 with PET

GSK1144814 is a potent, insurmountable antagonist at human NK₁ and NK₃ receptors. Understanding the relationship between plasma pharmacokinetics and receptor occupancy in the human brain, was crucial for dose selection in future clinical studies. GSK1144814 occupancy data were acquired in parallel with the first-time-in-human safety and tolerability study. [¹¹C]GR-205171 a selective NK₁ receptor PET ligand was used to estimate NK₁ occupancy at several time-points following single dose administration of GSK1144814. The time-plasma concentration-occupancy relationship post-single dose administration was assessed, and used to predict the plasma concentration-occupancy relationship following repeat dose administration. Repeat dose predictions were tested in a subsequent cohort of subjects examined following approximately 7 and 14 days dosing with GSK1144814. GSK1144814 was shown to demonstrate a dose-dependent occupancy of the NK₁ receptor with an estimated in vivo EC₅₀~0.9 ng/mL in the human brain. A direct relationship was seen between the GSK1144814 plasma concentration and its occupancy of the brain NK₁ receptor, indicating that in future clinical trials the occupancy of brain receptors can be accurately inferred from the measured plasma concentration. Our data provided support for the further progression of this compound and have optimised the likely therapeutic dose range.

Unexpectedly high affinity of a novel histamine H(3) receptor antagonist, GSK239512, in vivo in human brain, determined using PET

BACKGROUND AND PURPOSE

This study aimed to investigate the relationship between the plasma concentration (PK) of the novel histamine H3 receptor antagonist, GSK239512, and the brain occupancy of H(3) receptors (RO) in healthy human volunteers.

EXPERIMENTAL APPROACH

PET scans were obtained after i.v. administration of the H(3) -specific radioligand [(11) C]GSK189254. Each subject was scanned before and after single oral doses of GSK239512, at 4 and 24 h after dose. PET data were analysed by compartmental analysis, and regional RO estimates were obtained by graphical analysis of changes in the total volumes of distribution of the radioligand, followed by a correction for occupancy by the high affinity radioligand. The PK/RO relationship was analysed by a population-modelling approach, using the average PK of GSK239512 during each scan.

KEY RESULTS

Following administration of GSK239512, there was a reduction in the brain uptake of [(11) C]GSK189254 in all regions, including cerebellum. RO at 4 h was higher than at 24 h, and the PK/RO model estimated a PK associated with 50% of RO of 0.0068 ng·mL(-1) . This corresponds to a free concentration of 4.50 × 10(-12 ) M (pK = 11.3).

CONCLUSIONS AND IMPLICATIONS

The affinity of GSK239512 for brain H3 receptors in humans in vivo is much higher than that expected from studies in vitro, and higher than that observed in PET studies in pigs. The study illustrates the utility of carrying out PET studies in humans early in drug development, providing accurate quantification of GSK239512 RO in vivo as a function of time and dose.

Technologies: preclinical imaging for drug development

Preclinical imaging with magnetic resonance imaging (MRI), computerised tomography (CT), ultrasound (US), positron emission tomography (PET) or single-photon emission computed tomography (SPECT) enable non-invasive measures of tissue structure, function or metabolism in vivo. The technologies can add value to preclinical studies by enabling dynamic pharmacological observations on the same animal and because of possibilities for relatively direct clinical translation. Potential benefits from the application of preclinical imaging should be considered routinely in drug development.

Evaluation of 11C-GSK189254 as a novel radioligand for the H3 receptor in humans using PET

The histamine H(3) receptor is implicated in the pathophysiology of several central nervous system disorders. N-methyl-6-(3-cyclobutyl-2,3,4,5-tetrahydro-1H-benzo[d]azepin-7-yloxy)-nicotamide (GSK189254) is a highly potent, selective, and brain-penetrant H(3) receptor antagonist. Previous studies in the pig using PET have shown that (11)C-GSK189254 uptake in H(3)-rich regions of the brain can be blocked by the selective H(3) antagonist ciproxifan. The purpose of the present study was to evaluate (11)C-GSK189254 as a PET radioligand for human studies and to determine the dose-receptor occupancy relationship of GSK189254 in the human brain.

METHODS

Dynamic PET scans were obtained in healthy subjects over 90 min after intravenous administration of approximately 370 MBq of (11)C-GSK189254. Blood samples were taken throughout the scans to derive the arterial plasma parent input function. Each subject was scanned twice, either with tracer alone (test-retest) or before and after a single oral dose of GSK189254 (10-100 microg). Data were analyzed by compartmental analysis, and regional receptor-occupancy estimates were obtained by graphical analysis of changes in the total volumes of distribution (V(T)) of the radioligand.

RESULTS

(11)C-GSK189254 readily entered the brain; its regional brain distribution reflected the known distribution of H(3) receptors, with high binding in the caudate and putamen, intermediate binding in cortical regions, and low binding in the cerebellum. GSK189254 displayed a high receptor affinity, and a marked reduction in V(T) was apparent at all the doses tested. The oral dose equaling 50% occupancy of the available receptor sites (ED(50)) was estimated as 4.33 microg. Additional data on plasma pharmacokinetics after oral dosing and the plasma free fraction gave a corresponding estimate of the free concentration of GSK189254 required to occupy 50% of the available receptor sites (EC(50)) (0.011 nM). The test-retest data showed reductions in regional V(T) on the second scan in all subjects. A nonlinear compartmental analysis of this effect demonstrated that this reduction was consistent with carryover of a tracer mass dose effect with an estimated in vivo apparent dissociation constant of 0.010 nM, close to the independent estimate of the plasma EC(50).

CONCLUSION

(11)C-GSK189254 can be used to quantify H(3) receptor availability in humans in vivo using PET but requires high specific activity; the possibility of tracer mass dose effects should be carefully analyzed.

Vision and touch in ageing: Crossmodal selective attention and visuotactile spatial interactions

We investigated whether ageing affects crossmodal selective attention (the ability to focus on a relevant sensory modality and ignore an irrelevant modality) and the spatial constraints on such selective processing. Three groups of 24 participants were tested: Young (19-25 years), Young-Old (65-72 years) and Old-Old (76-92 years). The participants had to judge the elevation of vibrotactile targets (upper/index finger and lower/thumb), presented randomly to either hand while ignoring concurrent visual distractors. In a second task, the role of the target and distractor modalities was reversed. Crossmodal selective attention was assessed by comparing performance in the presence versus absence of distractors. Spatial constraints on selective attention were also investigated by comparing the effect of distractors presented on the same versus opposite side as the target. When attending to touch, the addition of visual distractors had a significantly larger effect on error rates in both of the older groups as compared to the Young group. This indicates that ageing has a detrimental effect on crossmodal selective attention. In all three age groups, performance was impaired when the target and distractor were presented at incongruent as compared to congruent elevations in both tasks. This congruency effect was modulated by the relative spatial location of the target and distractor in certain conditions for the Young and the Young-Old group. That is, participants in the two younger age groups found it harder to attend selectively to targets in one modality, when distractor stimuli came from the same side rather than from the opposite side. However, no significant spatial modulation was found in the Old-Old group. This suggests that ageing may also compromise spatial aspects of crossmodal selective attention.

Multicentre randomized-controlled clinical trial of Ipocol, a new enteric-coated form of mesalazine, in comparison with Asacol in the treatment of ulcerative colitis

BACKGROUND

5-Aminosalicylates remain important in the treatment of ulcerative colitis, but it is uncertain if the various preparations currently available are equivalent given the different delivery systems that exist. Generic prescription of mesalazine (mesalamine) is therefore inappropriate. Ipocol has recently become available as an alternative to Asacol-MR.

AIM

To compare the two agents in a controlled trial using a non-inferiority design.

METHODS

Eighty-eight ulcerative colitis patients with a mild to moderate clinical relapse were randomized to one of the two drugs at a daily dose of 2.4 g for 8 weeks. Safety was the key concern; the primary measured end-point was efficacy as judged from a colitis activity index.

RESULTS

There were no unexpected adverse events of clinical consequence. The colitis score improved similarly in both patient groups (by 2.3 with Ipocol and by 1.5 with Asacol: not significant), and a similar proportion was in clinical remission at the end of the study (26.1% for Ipocol and 28.6% for Asacol: not significant). Systemic steroids were needed in 11.9% of the Asacol-treated patients compared with 6.5% with Ipocol (not significant).

CONCLUSION

It appears appropriate to conclude that, while not identical to Asacol-MR, Ipocol offers a safe and similarly effective alternative.

249 EFFECT OF REFREEZING BULL SEMEN ON IVF SUCCESS RATE

Cryopreserved semen from valuable sires may be available in limited quantities in some situations. A large percentage of the spermatozoa in a thawed straw is potentially wasted since a relatively small number of spermatozoa are required for most assisted reproduction techniques. The goal of this study was to determine the effect of dilution and refreezing of bull semen on fertilization and blastocyst development rates following in vitro fertilization. The hypothesis was that frozen bull semen that was thawed, diluted, and refrozen could be used successfully for IVF. Oocytes were harvested from cow ovaries collected from a local abattoir and matured in vitro for 24 hours. Ova were subsequently assigned to one of four in vitro fertilization treatment groups. Group 1 ova (n = 158) were fertilized with bull semen frozen at a concentration of 20 × 106 spermatozoa per 0.25 mL straw. Group 2 ova (n = 157) were fertilized with semen frozen at an initial concentration of 2 × 106 spermatozoa. Group 3 ova (n = 157) were fertilized with semen that had been thawed and refrozen at a concentration of 20 × 106 spermatozoa. Group 4 ova (n = 150) were fertilized with semen that had initially been frozen at a concentration of 20 × 106 spermatozoa and then thawed, diluted to a concentration of 2 × 106 spermatozoa, and refrozen. IVF was performed in a medium volume of 100 μL using 1 × 106 spermatozoa/mL. Cleavage and blastocyst rates were determined 2 days and 7 days, respectively after IVF. Cleavage rates following IVF was highest with semen frozen at 20 × 106 spermatozoa (89.9%), intermediate with semen frozen at 2 × 106 spermatozoa or refrozen at 20 × 106 spermatozoa (71.3% and 73.9%, respectively), and lowest with semen refrozen at 2 × 106 spermatozoa (38.7%) (P < 0.05). Blastocyst development rate was not significantly different (P > 0.05) among treatment groups. This study confirmed the hypothesis that refrozen bovine semen can be used successfully for in vitro fertilization. Although the overall IVF efficiency was lower using diluted refrozen semen, multiple IVF procedures could theoretically be performed over time from one initial straw. Consequently, if a limited amount of frozen semen is available, thawing of a single straw followed by dilution, re-allocation into multiple straws, and refreezing should be considered to facilitate the more efficient use of semen in future assisted reproduction endeavors. This study was supported by the PEG Program, Colorado State University.

Organization of the promoter region of the human NF-IL6 gene

In monocyte/macrophages, the human NF-IL6 gene was activated by LPS or PMA. However, a robust response required stimulation of cells with both LPS and PMA. To examine the molecular basis of this response, we isolated human genomic DNA and determined the nucleotide sequence of a segment (6.4 kb) that included the transcription initiation site of the gene. The unique sequences in the 6.4-kb DNA include several potential transcription factor-binding elements that may explain the molecular basis of the activation of the human NF-IL6 gene by signaling molecules that control the immune and inflammatory responses. Deletion analysis localized an LPS+PMA responsive region downstream position -287, with respect to the transcription initiation site of the NF-IL6 gene. The responsive region includes a potential site for interactions with CREB and a region (-287 to -247) that interacts with SP1 and SP3. In functional assays, the potential CREB site responded to cellular stimulation. The region that interacted with SP1 and SP3 augmented the overall level of activity produced in response to LPS+PMA.

Modulatory effects of L-DOPA on D2 dopamine receptors in rat striatum, measured using in vivo microdialysis and PET

Putative modulatory effects of L-3,4-dihydroxyphenylalanine (L-DOPA) on D2 dopamine receptor function in the striatum of anaesthetised rats were investigated using both in vivo microdialysis and positron emission tomography (PET) with carbon-11 labelled raclopride as a selective D2 receptor ligand. A single dose of L-DOPA (20 or 100mg/kg i.p.) resulted in an increase in [11C]raclopride binding potential which was also observed in the presence of the central aromatic decarboxylase inhibitor NSD 1015, confirming that the effect was independent of dopamine. This L-DOPA evoked D2 receptor sensitisation was abolished by a prior, long-term administration of L-DOPA in drinking water (5 weeks, 170mg/kg/day). In the course of acute L-DOPA treatment (20mg/kg), extracellular GABA levels were reduced by approximately 20% in the globus pallidus. It is likely that L-DOPA sensitising effect on striatal D2 receptors, as confirmed by PET, may implicate striato-pallidal neurones, hence a reduced GABA-ergic output in the projection area. Since the L-DOPA evoked striatal D2 receptor supersensitivity habituates during long-term treatment, the effects reported here may contribute to the fluctuations observed during chronic L-DOPA therapy in Parkinson's disease.

In vivo saturation kinetics of two dopamine transporter probes measured using a small animal positron emission tomography scanner

When estimated in vitro, the parameters which describe the binding of radiolabelled analogues of cocaine to sites on the dopamine transporter are very much influenced by the methodology used. In the present study, a small animal positron emission tomography (PET) scanner was used to estimate in vivo saturation kinetics for two carbon-11 labelled compounds presently used to monitor dopamine terminal function. The binding of [11C]CFT (WIN 35,428) in rat striatum was adequately described by a single-site model, giving an apparent dissociation constant corresponding to an intravenous dose of 242 nmol/kg. In contrast, the binding of [11C]RTI-121 was better described by a two-site model with the 'high-affinity' site or state (dissociation constant = 1 nmol/kg) being significantly occupied at doses routinely used in PET scanning. Such findings cannot readily be predicted from in vitro work, but could aid in both the choice of ligand and the model used in quantification of scan data. While multi-dose in vivo PET studies are difficult in man, rat PET can easily be employed either pre-clinically for putative radioligands, or experimentally, to study drug interactions and receptor occupancy related to functional efficacy.

The effects of donor stage on the survival and function of embryonic striatal grafts in the adult rat brain. II. Correlation between positron emission tomography and reaching behaviour

Grafts of embryonic striatal primordia are able to elicit behavioural recovery in rats which have received an excitotoxic lesion to the striatum, and it is believed that the P zones or striatal-like tissue within the transplants play a crucial role in these functional effects. We performed this study to compare the effects of different donor stage of embryonic tissue on both the morphology (see accompanying paper) and function of striatal transplants. Both the medial and lateral ganglionic eminence was dissected from rat embryos of either 10 mm, 15 mm, 19 mm, or 23 mm crown-rump length, and implanted as a cell suspension into adult rats which had received an ibotenic acid lesion 10 days prior to transplantation. After four months the animals were tested on the "staircase task" of skilled forelimb use. At 10-14 months rats from the groups which had received grafts from 10 mm or 15 mm donor embryos were taken for positron emission tomography scanning in a small diameter positron emission tomography scanner, using ligands to the dopamine D1 and D2 receptors, [11C]SCH 23390 and [11C]raclopride, respectively. A lesion-alone group was also scanned with the same ligands for comparison. Animals which had received transplants from the 10 mm donors showed a significant recovery with their contralateral paw on the "staircase test". No other groups showed recovery on this task. Similarly, the animals with grafts from the youngest donors showed a significant increase in D1 and D2 receptor binding when compared to the lesion-alone group. No increase in signal was observed with either ligand in the group which had received grafts from 15 mm donors. Success in paw reaching showed a strong correlation to both the positron emission tomography signal obtained and the P zone volume of the grafts. These results suggest that striatal grafts from younger donors (10 mm CRL) give greater behavioural recovery than grafts prepared from older embryos. This recovery is due to both the increased proportion of striatal-like tissue within the grafts and an increase in functional D1 and D2 dopamine receptors measured by positron emission tomography, i.e. a more extensive integration of the graft with the host brain.

Evaluation in rat of RS-79948-197 as a potential PET ligand for central alpha 2-adrenoceptors

Tritium-labelled RS-79948-197 {(8aR,12aS,13aS)-5, 8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulphon yl)-6H-iso- quino[2,1-g][1,6]naphthyridine} was evaluated in rat brain as an in vivo ligand for central alpha 2-adrenoceptors, as a preliminary step in the development of a radioligand for positron-emission tomography (PET) studies. The maximal receptor-specific signal was achieved within 90-120 min after i.v. injection of [ethyl-3H]RS-79948-197 and was selective for the alpha 2- compared with the alpha 1-adrenoceptor, with no detectable binding to the imidazoline-I2 site. Estimates for binding potential (approximating to Bmax/Kd) ranged between 3.4 in entorhinal cortex and 0.5 in medulla oblongata. The results, which indicate a similarly localised but 2-fold increase in specific binding compared with that previously demonstrated using [3H]RX 821002 (2-methoxy-idazoxan), are sufficiently encouraging as to support further investment in the development of 11C-labelled RS-79948-197, or a close structural analogue, as a ligand for clinical PET.

The potential of high-resolution positron emission tomography to monitor striatal dopaminergic function in rat models of disease

The use of a recently commissioned small-diameter, high-resolution positron emission tomography (PET) to obtain a measure of specific binding of 3 carbon-11 labelled ligands in rat striatum is described. Using cerebellum as a reference tissue, compartmental modelling was used to obtain individual estimates of striatal binding potential (defined as the ratio of rate constants to and from the specifically bound compartment) for [11C]raclopride (D2 receptors), [11C]SCH 23390 (D1 receptors) and [11C]RTI-121 (dopamine transporter). The coefficients of variation in control, anaesthetized rats were of the order of 10%. Using two models of human disease, namely striatal injection of ibotenic acid to produce postsynaptic cell loss as in Huntington's disease, and 6-hydroxydopamine injection into substantia nigra pars compacta to mimic dopaminergic terminal loss in Parkinson's disease, marked reductions in binding potential were observed for the corresponding pre- or postsynaptic markers. When the regions of interest are so small as to be of the order of the spatial resolution of the system, factor such as spill over and partial volume negate absolute quantification of tissue radioactivity. Nevertheless, the use of PET to monitor relative changes in dopaminergic integrity should be considered as a viable complement to established in vivo microdialysis and post mortem techniques.

Development of central 5-HT2A receptor radioligands for PET: comparison of [3H]RP 62203 and [3H]SR 46349B kinetics in rat brain

[3H]RP 62203 and [3H]SR 46349B binding were assessed in rat brain after intravenous (iv) injection. The distribution of specific binding of each radioligand corresponded to the known distribution of 5-HT2A receptor sites. The maximum signals (counts/g tissue over counts/g cerebellum) given by [3H]RP 62203 and [3H]SR 46349B were 9.0 +/- 0.9 at 60 min and 3.2 +/- 0.3 at 30 min, respectively, in frontopolar cortex. Specific binding was quantified using a reference-tissue compartment model. RP 62203 appears to be more suitable than SR 46349B for development as a PET radioligand on the basis of its higher receptor specific signal.

Evaluation of [11C]RTI-121 as a selective radioligand for PET studies of the dopamine transporter

The cocaine analogue RTI-121 (3 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid isopropyl ester), when labeled with carbon-11, was evaluated in rats as a potential PET ligand for the dopamine transporter. The compound gave in vivo striatum:cerebellum ratios that were similar to those obtained with the related ligand [11C]RTI-55 (2 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid methyl ester) but showed a much greater selectivity for the dopamine compared with the 5-HT uptake site. The results indicate that [11C]RTI-121 could be used in preference to [11C]RTI-55 in man. Experimentally, [11C]RTI-121 has potential in the quantification of dopamine terminal function in rat models of disease, using a combination of autoradiography, postmortem sampling, and in vivo tomography.

Lack of permanent nigrostriatal dopamine deficit following 6-hydroxydopamine injection into the rat striatum. Short communication

The lesion caused by a single 6-hydroxydopamine injection into rat striatum was evaluated. In vivo positron emission tomography using a dopamine reuptake tracer revealed no consistent reduction in striatal dopamine transporter. Amphetamine rotation test was negative up to 18 weeks. A 21% reduction in striatal dopamine seen at 11 weeks was not detectable at 18 weeks. Tyrosine hydroxylase-positive neurone counts showed no decline in substantia nigra. Our results suggest that this lesion may be subject to compensation and therefore should be used with caution in studies on neuroprotective treatments of Parkinson' disease.

GDNF protects against 6-OHDA nigrostriatal lesion: in vivo study with microdialysis and PET

We have investigated whether glial cell line-derived neurotrophic factor (GDNF) protects against a complete unilateral 6-hydroxydopamine (6-OHDA) nigrostriatal lesion, a robust rat model of Parkinson's disease. GDNF or vehicle were administered above the rat substantia nigra and into the lateral ventricle immediately before an ipsilateral 6-OHDA injection into the medial forebrain bundle. In vivo tests were employed to assess the effects of the treatment: microdialysis to measure striatal dopamine release, amphetamine challenge to estimate turning behaviour, and positron emission tomography (PET) to image dopamine reuptake sites. The present results show that GDNF can protect dopaminergic neurones against an acute and irreversible 6-OHDA lesion. They are encouraging for potential use of GDNF in Parkinson's disease.

Assessment of striatal graft viability in the rat in vivo using a small diameter PET scanner

A small diameter positron emission tomography (PET) scanner has been used to monitor [11C]raclopride (D2 receptor) binding in vivo in either intact striatum, denervated striatum following an excitotoxic lesion with ibotenic acid, or lesioned and grafted striatum following implantation of cortical or striatal tissue grafts in rats. Binding of [11C]raclopride was localized in the intact striatum within 20 min of injection of the radioligand, and was much reduced within the lesioned striatum. Cortical grafts exhibited a similar low level of binding to the lesioned striatum, whereas striatal grafts showed specific binding at an intermediate level. The [11C]raclopride binding signal in vivo correlated well with the extent of surviving or grafted striatal tissue observed post morten by Nissl staining and acetylcholinesterase histochemistry. Thus, the distribution of dopamine receptors as seen in the PET scanner are consistent with post mortem anatomical observations of striatal, lesion and graft sizes, and suggest that PET can provide a useful tool for monitoring the viability of implanted striatal graft tissues in vivo.

Effect of L-dopa and 6-hydroxydopamine lesioning on [11C]raclopride binding in rat striatum, quantified using PET

A positron emission tomograph (PET) was used to image D2 dopamine receptor function in rat striata and to obtain regional time-radioactivity curves from individual rat brains following i.v. injection of carbon-11-labelled raclopride. Despite the limited resolution of the camera, together with associated spillover and partial volume effects, the kinetic data obtained from striata were such that specific binding of the radioligand could be quantified unilaterally, using a reference tissue compartmental model, with cerebellum data as an indirect input function. With the exception that the rat is anaesthetised, the experimental system is analogous to the acquisition and collection of clinical PET data and, by using animal models of disease, can be used to aid the interpretation of clinical studies. Using 6-hydroxydopamine (6-OHDA) lesioning of the substantia nigra pars compacta to produce a rat hemiparkinsonian model, the present results confirm that deafferentation causes a supersensitivity of post-synaptic D2 dopamine receptors. Saturation studies indicated that the measured 23% increase in [11C]raclopride binding potential reflected a change in receptor affinity. Modulation of extracellular dopamine concentration, monitored by in vivo microdialysis, demonstrated that the increased binding was unlikely to be due to a reduction in receptor occupancy by endogenous dopamine. Acute administration of L-3,4-dihydroxyphenylalanine (L-dopa) also caused an increase in [11C]raclopride binding potential, confirming the suggestion that L-dopa plays a more complex role than that of dopamine precursor in the nigrostriatal pathway.

The design and physical characteristics of a small animal positron emission tomograph

A small diameter positron emission tomography, designed specifically for small animal studies, was constructed from existing, commercially available, bismuth germanate (BGO) detectors and electronics. The scanner consists of 16 BGO detector blocks arranged to give a tomograph with a diameter of 115 mm and an axial field of view (FOV) of 50 mm. Each block is cut to produce eight (axial) by seven (radial) individual detector elements. The absence of interplane septa enables the acquisition of 3D data sets consisting of 64 sinograms. A 2D data set of 15 sinograms, consisting of eight direct and seven adjacent cross planes, can be extracted from the 3D data set. Images are reconstructed from the 2D sinograms using a conventional filtered backprojection algorithm. Two methods of normalization were investigated, based on either a rotating 68Ge rod source, or a uniform 68Ge plane source, with a uniform cylindrical 18F phantom. Attenuation of the emitted photons was estimated using a rotating 68Ge rod source. The transaxial resolution of the tomograph was measured as 2.3 mm full width at half maximum (FWHM) and 5.6 mm full width at tenth maximum (FWTM) at the centre of the FOV, degrading to 6.6 mm (radial) and 4.4 mm (tangential) FWHM and 10.4 mm (radial) and 14.4 mm (tangential) FWTM at 40.0 mm from the centre of the FOV. The axial slice width was 4.3 mm FWHM, 10.3 mm FWTM at the centre of the transaxial field of view and 4.4 mm FWHM, 10.6 mm FWTM at 20.0 mm from the centre of the FOV. A scatter fraction of 31.0% was measured at 250-850 keV, for an 18F line source centred in a 60 mm diameter, water-filled phantom, reducing to 20.4% and 13.8% as the lower energy discrimination was increased to 380 keV and 450 keV, respectively. The count rate performance was measured using a noise equivalent count rate method, and the linearity of the dead time correction was confirmed over the count rates encountered during routine scanning. In 2D mode, the absolute sensitivity of the tomograph was measured as 9948 counts s-1 MBq-1 at 250-850 keV, 8284 counts s-1 MBq-1 at 380-850 keV and 6280 counts s-1 MBq-1 at 450-850 keV.

Evaluation of [O-methyl-3H]WAY-100635 as an in vivo radioligand for 5-HT1A receptors in rat brain

N-(2-(4-(2-Methoxyphenyl)-1-piperazinyl)ethyl)-N-(2- pyridyl)cyclohexanecarboxamide trihydrochloride (WAY-100635) is a new, potent and selective 5-HT1A receptor antagonist. We have evaluated radiolabelled WAY-100635 as a prospective radioligand for positron emission tomography (PET) by studying biodistribution in rat ex vivo. After intravenous injection, [O-methyl-3H]WAY-100635 cleared rapidly from plasma but was retained in brain. Specific binding was quantified from kinetic studies, using a reference-tissue compartment model, fitting for binding potential (k3/k4). The regional variation in binding potential correlated with the known distribution of 5-HT1A receptors. Saturation studies gave Bmax values in vivo that were consistent with those reported in vitro. At 60 min after injection, the ratio of radioactivity in 5-HT1A receptor-rich regions (e.g. septum, entorhinal cortex and hippocampus) to that in cerebellum reached approximately 16. Pre-dosing the rats with WAY-100635 (2 mg/kg) reduced this ratio to one, whereas similar pre-dosing with citalopram (5-HT uptake site inhibitor), prazosin (alpha 1A-adrenoceptor antagonist) or idazoxan (alpha 2-adrenoceptor antagonist) caused little or no reduction. Substantial (77%) blockade of [3H]WAY-100635 binding was achieved with the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and the partial agonists, ipsapirone and buspirone. Thus, the properties of WAY-100635 are such that, when labelled with carbon-11, it could provide a radioligand suitable for clinical and pharmacological investigations of central 5-HT1A receptors in man using PET.

Synthesis of the enantiomers of [N-methyl-11C]PK 11195 and comparison of their behaviours as radioligands for PK binding sites in rats

The enantiomers of [N-methyl-11C]PK 11195, a radioligand for PET studies of PK (peripheral benzodiazepine) binding sites, have been prepared from the newly synthesized N-desmethyl-enantiomers by 11C-methylation with N.C.A. [11C]iodomethane. The brain uptake and retention of each enantiomer was compared with that of the racemic radioligand after i.v. administration into normal rats and into rats with focal cortical lesions. No significant differences in the uptakes of the enantiomers were observed in regions devoid of PK binding sites. However, the R-enantiomer was retained to a significantly greater extent than the S-enantiomer in olfactory bulbs-tubercles, which contain some PK binding sites, and also in 9-day-old focal cortical lesions, which are greatly enriched in PK binding sites associated with macrophage infiltration. The observed differences are consistent with the approximately 2-fold greater affinity of the R-enantiomer for PK binding sites reported in vitro and imply that the use of this enantiomer would have advantages over the use of the racemate currently used for PET studies.

Transposon mutagenesis in Legionella pneumophila. I.--Persistence of suicide and broad host-range plasmids

Two of three highly virulent strains of Legionella pneumophila could act as recipients at high frequencies in conjugation experiments with Escherichia coli donor strains carrying broad host-range plasmids belonging to incompatibility groups N, P and W. All broad host-range and most transposon-delivery plasmids persisted within transconjugants with high stability. Only one (pSUP1021) of several vehicles designed for the delivery of transposons into the chromosome of Gram-negative bacteria was found to yield transposon mutants of Legionella at a detectable frequency.

Intralesional interferon therapy for basal cell carcinoma

In a clinical trial of 172 patients at four medical centers, interferon alfa-2b (1.5 x 10(6) IU) or a placebo was injected directly into biopsy-proved noduloulcerative or superficial basal cell carcinomas three times weekly for 3 weeks, for a cumulative dose of 13.5 million IU. Efficacy of treatment was determined at 16 to 20 weeks by examination of biopsy specimens that demonstrated cure of lesions in 86% of interferon-treated patients and in only 29% of placebo-treated patients. During the treatment course and follow-up, an initial inflammatory response was observed at the treatment sites, followed by diminished erythema, improvement in overall appearance, and a decrease in size of lesions. Side effects of treatment, mainly flu-like symptoms, were usually mild and transient and occurred more commonly in the interferon-treated group. Only three patients, all in the interferon-treated group, discontinued therapy because of side effects. One year after initiation of therapy, 81% of interferon recipients and 20% of those given the placebo remained tumor free. Noduloulcerative and superficial lesions were equally responsive to treatment with interferon. For some patients with noduloulcerative or superficial basal cell carcinomas, intralesional interferon alfa-2b may be an alternative, effective treatment.